The present invention relates to a display apparatus, and more particularly to a display apparatus which is dynamically driven by a time-division system.
The display apparatus of a dynamic driving type employing the time-division system requires digit information for selecting a digit to be displayed and display information to be supplied to the selected digit. Since the digit signals are selectively sent to the display elements at the respective digits, independent signal lines must be separately provided to the respective display elements. On the other hand, the display information signals are transmitted through common signal lines to all the display elements in common. This dynamic driving is effective for a multidigit display apparatus employing, as display elements, fluorescent display panels, plasma display panels, light emitting diodes, or the like. In the multidigit display apparatus of the dynamic-driving type, the digit signal must be applied to the display element at the selected digit only at one instant. If not, erroneous display at the adjacent digits would occur, because the display information signal is applied to the display elements of all the digits in common. Especially, the shapes of the rising edge and the falling edge of the digit information signal pulse should be sharp in order to prevent erroneous display at the adjacent digit. However, the apparatus inevitably has both the stray capacitances of display elements and the wiring capacitances of the signal lines. These capacitances force rise and fall of the digit signal pulse to become slow. Therefore, it is very difficult to prevent overlap of one digit signal pulse with the adjacent digit signal pulses. It has accordingly been common practice to shorten the active period of each digit signal pulse in consideration of the rise time and/or fall time thereof. With the shortened active period, the overlap of the digit signal pulses can be avoided.
However, when the active period is markedly shortened, the display luminance is also markedly lowered to make the recognition of the displayed content difficult. Moreover, the rise time and/or fall time of the digit signal pulses are not always constant, but they depend upon the lengths of the corresponding signal lines and the number of the display elements to be coupled to the signal lines. This brings about the disadvantage that a large number of digit signal control circuits for controlling the active periods conforming with the kind of the display elements and the number of the display elements are needed.
The deterioration in rising and falling characteristics of the signal pulses arises, not only for the digit information signals, but also for display information signals. In case of driving a large-sized display apparatus, these two signals with deteriorated rising and falling characteristics frequently give rise to a flickering of the display, erroneous display, double display, etc.